Telephone call-wire circuits



Patented 311118 28, 15321.

l. F. TGOVIEY.

TELEPHONE CALL WIRE CIBCUfTS.

APPLICTSON HLED JUNE I0, 1919-r` lNVENTOR JQWW BY A ATTRNEY UNITED STATES PATENT FFQE..

JOHN F. TOOMEY, OF NEW YGRII, N. Y., ASSGNOR T0 AMERICAN TELEPI-IGNE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

TELEPHONE CALL-WIRE CIRCUITS.

Application led June 10,

To all whom 'it may concern.'

Be it known that I, JOHN F. TooMEY, residing at New York, in the county of New York and State of New York, have invented certain Improvements in rllelephone Call- VVire Circuits, of which the following is a specification.

This invention relates to telephone circuits, and more particularly to telephone call wire circuits.

In practice upon the occasion of a subscriber wishing to converse with another subscriber and making` known his desire to an operator at a central oflice, if the called subscriber is found to be connected with that particular oiiice, the call may be completed thereat. If, however, the line of the desired subscriber be connected to a distant otiice, it is necessary that a common conductor shall be provided between the two offices with which the lines of both subscribers may be connected, and which thus furnishes a link of communication commonly known as a trunk line. It is also necessary to provide means whereby an operator at a central oftice is enabled to communicate with another operator stationed at a dist-ant otiice in order that the said second operator may assign to the central ofiice operator which one of the trunk lines it is desired shall be employed for the connection. For this purpose at each initiating operators position there are provided a plurality of keys or buttons, each adapted when operated to complete a circuit to a distant otlice. These are ordinarily termed call wire circuits. ln previous call wire systems, the circuits were so arranged that either one or all the operators in the same oiiice could bridge their telephone sets across the call wire circuit at the same time. This feature caused considerable trouble, because the connection of a large number of operators sets to the call wire circuit at the` same time reduced the transmission efhciency to a point where it was difficult to pass calls over the circuit. @ne of the cardinal features of this invention consists in the provision of means whereby a call wire circuit is adapte-d to be used by only one operator at a time, the circuit being,` rendered inoperative at such time to a second operator and thereby providing higher transmission etticiency. Other and further features of the invention will hereinafter appear.

This invention may now be more fully Specification of Letters Patent.

Patented J une 28, 1921.

1919.v Serial No. 303,054.

.understood by reference to the accompanying drawing, in which one embodiment `is diagrammatically illustrated.

ln the arrangements of the invention there are shown twoftelephone switchboard positions 5 and G, together with the essential elements pertaining' to this improved circuit. While but two positions are illustrated, it will be understood that a plurality of positions may be provided at a central office, and each position be connected to an outgoing call wire circuit, comprisingl conductors 7 and 8 which terminate at a distant oiiice. .At each position there is provided switching means in the form of a call wire key or button, as indicated at 9 and l0. Associated with each call wire button is a position relay as represented by ll and l2 at positions 5 and 6. ln series with, and coinmon to said position relays is relay 13. rlhis relay is of suiiiciently high resistance so that but one position relay can operate in series with it at one time. The resistance of the position relays is made as low as possible in order to provide a low resistance shunt to ground to prevent the operation of a second position relay. Therefore, upon the depression of an initial call order button a circuit is provided by way of the position relay individual to said button and common relay 13 which operates both relays. rlhe operation of the position relay causes it to attract its armatures, thereby disconnecting` the operators set from the talking key and providing for the connection of said set with the order wire circuit. The operation of the relay 13 also connects battery through the back contacts of the other position relays to all of the busy signal lamps associated with the call wire key at the different switchboard positions, except the one where the operator is usingI the circuit. The busy lamp at this position will not light, because circuit is opened by the operation of the position relay thereat. The lighting of the lamps will thus inform the operators at the other' positions that the call wire circuit is being used. Should the operators ignore the busy signal and attempt to use the call wire circuit they will be unable to do so, because their individual position relay cannot be operated on account of the low resistance ground that is connected with the common signaling relay 13 by the operation of the first call wire key. Furthermore, owing,` to

the high resistance of the common signaling relay 13, there would not be suicient current to operate the second position relay.

The details of this circuit may be more sufficiently understood from the following description of its operation.

Th operator at position 5 upon desiring to communicate with a distant office will depress the call order wire key 9 which willl complete the following circuit: from ground, through said key 9, conductor 16, winding of relay 11, conductors 17 and 18, winding of relay 13 to grounded battery. rlhis circuit will provide for the energization of relays 11 and 13. The operation of relay 11 will cause it to attract its armatures, br aaking the circuit .with the talking key and providing for a circuit from the operators telephone set by way of conductors 19 and 20 through the armatures of relay 11 and conductors 7 and 8 of the call wire circuit, and thence to the distant oliice. The operator at position 5 is thus enabled to communicate with the operator at the distant station, who will make an assignment olf a certain trunk, whereupon the initiating' operator and distant operator will associate the plugs of the calling and called lines, respec-tively, with said trunk, thereby establishing a connection between the stations.

Upon the operation of common relay 13 its armature will be attracted and a circuit provided from ground, lamp 15, conductor 21, upper armature of relay 12 conductors 22 and 23, armature and contact of relay 13 to grounded battery. This circuit will provide for the lighting ot the lamp 15 at position 6 and the operator thercat will be informed that the call order wire is being used. if the operator at position 6 should ignore the busy signal 15, and should operate key 10 at the same time that key 9 was operated the relay 12 would not operate to connect the operators set at position 6 to conductors 7 and 8. The relay 12 could not operate at the same time While relay 11 was energized because a low resist-ance shunt to ground is provided by the operation of relay 11 over conductor 17, winding of relay 11, conductor 16, contact of key 9, to ground. Furthermore, while there is sufhcient current in the circuit closed upon the depression of key 9 to operate relay 11, the circuit closed by the simultaneous depression of key 10 will increase the resistance to such a degree as to prevent the operation or" relay 12. There will be, however, sufficient current in said circuit to maintain the relay 11 in its actuated condition. A like condition would prevail should any other operator at the associatedpositions ot the switchboard ignore the busy signal at her position.

lhile the arrangements of this invention have been illustrated as embodied in certain specific arrangements which have been deemed desirable, it will be understood that they are capable ot embodiment in many and widely varied `forms without departing` from the spirit of the invention as defined in the appended claim.

Having thus described the invention, what is claimed is:

In a telephone system comprising a plurality oi' switchboard positions, a call order wire associated with said positions, switching means at each oiz said positions, signaling means at each position, a relay common to all of said positions and in series with said switching means, means controlled by the switching means at each position for completing a circuit tor the relay at said position and said common relay, means controlled by said position relay ior connecting said order wire to said position, means controlled by said position relay and said common relay for preventing the simultaneous operation of any of the other of said relays, and means controlled by said position relay and com- `mon relay for operating the signaling means JOHN l?. TGOMEY. 

